A system in which a plurality of devices network-connected operates in coordination with one another is required to match control timings of the devices by matching times measured by the devices. Matching the control timings of a number of devices with each other is called timing synchronization.
For example, in a system in which a material is cut while the material is carried, a desired part of the material is cut even while the material is currently carried when the timing at which one device carries the material matches the timing at which another device cuts the material.
However, a part different from the desired part of the material is adversely cut if the timing at which the one device carries the material does not match the timing at which the other device cuts the material.
In a system requiring timing synchronization, in general, a synchronization master device that is a master for the timing synchronization and a synchronization slave device that is a slave for the timing synchronization communicate with each other at a predetermined communication time interval. In this situation, the synchronization slave device performs timing synchronization with the synchronization master device.
However, the accuracy of timing synchronization is decreased in some cases where a transmission time interval of transmit data of the synchronization master device fluctuates. Fluctuation in the transmission time interval is caused by a failure of the synchronization master device or a disturbance from a device or devices other than the synchronization master device, for example.
As a related technique, Patent Literature 1 listed below discloses a time synchronization device including: a plurality of estimated time calculation units that calculates an estimated time of a corresponding time master device among a plurality of time master devices each transmitting a reference time indicating a time to be a reference, on the basis of the reference time transmitted from the corresponding time master device and a propagation delay time from the time master device; and a current time calculation unit that calculates a current time meaning a current time point on the basis of a number of estimated times calculated by the plurality of estimated time calculation units, wherein the estimated time calculation unit discards a reference time transmitted from the corresponding time master device when the reference time is received at a reception interval longer than or equal to a threshold value (claim 5).